Field of the Invention
Various embodiments of the present invention relate to improvement in fuel-efficiency during a temporary stop, and more particularly, to a vehicle and a method for improving fuel-efficiency during a temporary stop capable of improving both of fuel-efficiency and noise, vibration, hashness (NVH) by reducing planetary gear noise and vehicle vibration which occur at the time of a neutral control during a D-stage temporary stop.
Description of Related Art
Generally, an automatic transmission for a vehicle includes a shift control apparatus which automatically controls a shift ratio depending on a driving speed and a load of a vehicle, in which the shift control apparatus controls a plurality of clutches and brakes, which are installed in a gear train, in an operation state or a non-operation state to control an RPM of an output stage of a planetary gear, thereby performing a shift.
In particular, under the condition that the improvement in fuel-efficiency of a vehicle has emerged as a very important issue, efforts to improve fuel-efficiency of an automatic transmission vehicle have been conducted. An example of the efforts may include a neutral control method.
The neutral control is a control method of making a clutch in a half neutral state at the time of a D-stage temporary stop in the automatic transmission vehicle configured of planetary gear sets to lower an engine load and lower fuel consumption, thereby improving the fuel-efficiency.
However, the neutral control brings about a rotating planetary gear set by a clutch release among the planetary gear sets which are not rotating by making the clutch in the half neutral state at the time of the D-stage temporary stop to which the neutral control is not applied and induces the gear noise due to the rotation of the planetary gear set. Therefore, at the time of the D-stage temporary stop in the automatic transmission vehicle configured of the planetary gear sets, the neutral control cannot but improve the fuel-efficiency but induce the planetary gear noise.
Usually, the planetary gear noise at the time of the neutral control may be improved by reducing a D-stage engine RPM at the time of the temporary stop and thus reducing the rotation of the planetary gear.
However, since the automatic transmission configured of the planetary gear sets does not usually use the neutral control at the time of the D-stage temporary stop, the D-stage engine RPM is set to be high to avoid a resonance frequency of a vehicle, and thus the low D-stage engine RPM for the neutral control at the time of the D-stage temporary stop cannot but coincide with the resonance frequency of the vehicle and the neutral control implementing vehicle brings about the vehicle vibration due to the coincidence with the resonance frequency of the vehicle.
Therefore, to improve the fuel-efficiency of the automatic transmission vehicle configured of the planetary gear sets, there is a need to solve two conflicting phenomena of the low D-stage engine RPM to reduce the planetary gear noise and the avoidance of the resonance frequency of the vehicle bringing about the vehicle vibration at the time of the neutral control.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.